Modern data storage devices such as disc drives are commonly used in a multitude of computer environments to store large amounts of data in a form that is readily available to a user. Generally, a disc drive has a magnetic disc, or two or more stacked magnetic discs, that are rotated by a motor at high speeds. Each disc has a data storage surface divided into a series of generally concentric data tracks where data is stored in the form of magnetic flux transitions.
A data transfer member (sometimes referred to as a read/write head) such as a magnetic transducer is moved by an actuator assembly to selected positions adjacent the data storage surface. The active elements of the read/write head are supported by suspension structures extending from the actuator assembly. The active elements are maintained a small distance above the data storage surface as the read/write head flies upon an air bearing generated by air currents caused by the spinning discs.
Each read/write head is typically provided with separate read and write elements, with a common configuration utilizing a thin film, inductive write element and a magneto-resistive (MR) read element. Data are written by passing a write current through the write element, with the write current generating a time-varying magnetic field which accordingly magnetizes the disc surface. Previously written data are read using the read element to transduce the selective magnetization of the disc to generate a read signal, which is received by a read channel to reconstruct the data.
The actuator assembly operates within a negative feedback, closed-loop servo system. Servo information is preliminarily written in the form of servo tracks that permit the read/write heads to be properly positioned during data reading and writing operations. A servo controller samples the position of the read/write heads relative to the servo track information and generates an error signal based upon the difference between the actual position and the reference position. This error signal is then used to drive the data head to the desired reference point, typically by demanding a current through a voice coil motor (VCM) which forms a part of the actuator assembly.
As data storage areal density has increased, the precision with which the servo track data must be written has become more important. Many mechanical vibrations, which hitherto could be ignored as negligible, produce disturbances that can result in erratic or distorted servo tracks. Such distortion can produce increases in error position signals, leading to unacceptable margin losses when attempting to seek or follow a particular servo track. This results in drive performance degradation, decreased capacity and increased reading and writing failures.
One of the prominent sources of disturbances is disc resonance and resonance imparted to the head and gimbal assembly. Many attempts have been made at modifying the amplitudes and frequencies of such resonances to prevent the associated adverse effect on servo track writing. Many attempts have also been made to improve servo track writing devices and associated methods, so as to stabilize the process.
One proposed solution is to perform the servo track writing operations within a helium environment, which affords a relatively more stable environment imparting less resonance on the disc and actuator assembly. It has been determined, however, that significant process improvements are possible by understanding the characteristics of the read/write head fly height within a controlled environment. Generally, servo tracks can be written more accurately by flying the head closer to the data storage medium. Also, it is possible to increase the throughput of a servo track writer apparatus by increasing the speed of the data storage medium during servo track writing within a less dense gaseous environment for a particular fly height. It is to these improvements and others as exemplified by the description and appended claims that embodiments of the present invention are directed.